HUMAN FACTORS

The Causal Relationship of Human Factors On A Negligent Discharge
Springfield Armory XD-40

There are three significant aspects that contribute to the safe use of a firearm: System Knowledge, Operational Training and Human Factors. While all three components are equally important it is Human Factors that is the least understood.

Commonly in litigation the only aspect of human factors that is looked at is attitude (state of mind) but there is a significantly less understood aspect – the Operator/Machine/ Environment paradigm.

We were retained by a client that was charged with first degree murder for killing his wife as a result of a gunshot wound to the head. The client swore the gun went off by itself and that he had no intent to harm his wife.

In a situation where the firearm itself may be in question we always begin by having the firearm taken from the evidence locker and thoroughly checked by our gunsmith. It was determined that the Springfield Armory XD-40, a .40 caliber, semi-automatic pistol, was in proper working condition.

We brought a Springfield Armory XD-40 similar to the one in the case to an interview with the client and asked him to demonstrate what happened leading up to the firearm’s discharge. The client displayed very poor safety procedures, a lack of firearm muzzle control and a marginal understanding of how the firearm worked.

There are six human factors issues that relate to a potential accidental discharge.

The client’s hand was too small to operate the firearm properly.

FIGURE 1: Loaded Chamber Indicator with right end tilted up indicating the firearm is loaded.

The client had no training in the operation of the firearm.

The Springfield Armory XD-40 has a loaded chamber indicator in the form of a small tab with the rearward facing end elevated when there is a cartridge chambered (Figure 1).

There is a safety on the upper rear of the grip that must be depressed for the firearm to fire. It is normally held down with the proper application of the handgrip (Figure 2).

FIGURE 2: Grip Safety which is held down when the hand grips the firearm properly.

There is a trigger safety built into the front of the trigger that requires the finger to contact it and press reward (Figure 3).

FIGURE 3: Trigger safety

The magazine release is a button directly behind the trigger on the left side of the firearm (Figure 4). The magazine release button goes through the grip of the firearm and is accessible on the right side of the firearm (Figure 5). It allows a gun smith to reverse the mechanism making it a left handed firearm.

The client said he’d owned the firearm for about a year, never used it and had sold it. His intent was to clean the firearm, put it back in the original case and have it ready to be picked up. When his wife handed him the firearm he noticed the Loaded Chamber Indicator signaled there was a live cartridge in the firearm.

The client’s hand was not large enough to properly hold the firearm and simultaneously depress the magazine release button with his thumb (Figure 6).

FIGURE 6: Firearm too large for the hand causing the thumb to fall short

To resolve the problem the client shifted the firearm in his hand bringing his thumb over the magazine release which he attempted to depress. In doing so, his index finger shifted position as he shifted the firearm in his grip and positioned itself directly over the righthand side magazine release (Figure 7).

FIGURE 7 By shifting his grip to be able to operate the magazine release button with his thumb it also moves the index finger rearward and it falls on the magazine release button on the right side.

The harder he pushed with his thumb the tighter his grip had to be to accommodate it which included his index finger unwittingly pushing the magazine release on the right side of the firearm in opposition to the pressure being exerted by his thumb: His thumb was pushing against his index finger.

FIGURE 8 To get a solid grip while using the left thumb to push on top of the right thumb, the left index finger gripped inside the trigger guard close to the trigger and accidentally pressed it.

By shifting the firearm in his grip the palm of his hand moved across the upper rear grip safety and though it was not a proper grip it nevertheless was held down by the palm which removed the block which would have otherwise prevented the trigger from being depressed.

In his frustration at being unable to make the magazine release function properly he pressed harder and then positioned his left thumb on top of the right thumb to increase the amount of force. To gain leverage to do it he hooked his left index finger in the trigger guard (Figure 8) and at some point his left index finger contacted the trigger and the firearm discharged.